Replaceable drill tips and cutting inserts are used in connection with various bits, shanks and tool holding apparatus in machine tooling for metal working. Replaceable tips eliminate the need to replace and exchange entire tools in continuous drilling and milling operations. For speed and efficiency, the manner of connection of replaceable tips with the holder or shank must be relatively simple, yet extremely rigid and strong to withstand the forces of moving metal-to-metal contact. The manner of engagement with a cutting or milling tip with the tool holder is somewhat dependent on the configuration of the cutting tip. In the case drill tips, there is typically a generally cylindrical drill shank with a distal end to which a tip is attached, so there is abutment of two circular faces of the tip and shank and very high torsional and lateral forces at the interface.
On a drill bit of this type, a cutting head is detachable fixed to a drill shaft. German Patent No. 196 05157 A1 describes a drilling tool of the prior art in which the cutting head projects by means of a stud into a receiving recess on the face of the drill shaft, where it is fixed in position with a screw that is oriented at a right angle to the longitudinal axis of the drill. On a drilling tool of the prior art described in TWO 98/53943, the drilling head is fixed in position in the drill shaft with a free fit that acts in the axial direction and in the direction of rotation of the drill.
A weakness of the prior art is in the strength and alignment of the attachment mechanism between drilling and cutting tips and the tool holder or shank. An attachment design which affords perfect alignment and positioning and which has sufficient strength is very desirable.